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#/bin/bash

# total number of cores available
N=64

# we do not expect NWChem to scale to more than 8 threads per process
for P in $((N)) $((N/2)) $((N/4)) $((N/8)) ; do
  T=$((N/${P}))
  export OMP_NUM_THREADS=${T}
  mpirun -n $P ...
done

NWChem input file tuning

The CCSD(T) semidirect and TCE modules have at least one important tuning parameter.

DFT module

The DFT module contains no OpenMP and has limited tuning options, most of which related to quantum chemistry algorithms that can be ignored for the SCC. The most important tuning options related to ARMCI and MPI library choice, as described above.

TCE CCSD(T) module

See https://nwchemgit.github.io/TCE.html#maximizing-performance for details. The most important tuning parameters are:

• 2eorb always use this

• 2emetset to 13 and see how that works

• tilesizethe default for CCSD(T) should be 20. If you set it to a much larger value, the job will crash. Smaller values are usually less efficient. You can also try https://nwchemgit.github.io/TCE.html#ccsdtcr-eomccsdt-calculations-with-large-tiles instead and see if that helps performance.

Semidirect CCSD(T) module

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Run the application with the below input and submit all logs, build & run scripts from your best run.

Semidirect CCSD(T)

The input file that follows (generated with ./make_nwchem_input.py w7 rccsd-t cc-pvtz energy) is the one that must be used. The only lines that you can change are noted as such.

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